An aircraft ice protection method commonly comprises anti-icing steps and deicing steps designed to defend an airfoil from undue ice accumulation during flight. An electrothermal device is disposed on, and/or integrated into, the airfoil. Ice protection steps are performed by controlling the initiation, the duration, and/or the level of electrical power supplied to device's heating elements.
During anti-icing steps, the electrothermal device continuously heats an airfoil region to a temperature above freezing, whereby ice cannot form thereon. During deicing steps, the electrothermal device intermittently heats an airfoil region on which ice has been allowed to accumulate. The to-be-deiced region need only be heated enough to melt the adhesion layer between the airfoil surface and the accumulated ice. Once this airfoil-to-ice bond is broken, the ice fragments into pieces which are easily swept away by the oncoming airstream.
Deicing is more power affordable than anti-icing because intermittent heating steps require significantly less electrical energy than continuous heating steps. And intermittent steps allow staggered zone-heating whereby power draws can be somewhat regularized. If deicing is not appropriate for an airfoil region (e.g., the leading edge region), the corresponding heating area of the electrothermal device (e.g., the parting strip) is usually sized as small as possible to conserve power.